This invention relates to a disc cartridge casing for packaging a disc cartridge comprised of a recording disc, such as an optical disc of a magneto-optical disc, contained in a main cartridge body. More particularly, it relates to a sleeve casing for a disc cartridge and a method for packaging the sleeve casing with the disc cartridge therein.
A so-called sleeve casing has been proposed as a casing for packaging the disc cartridge comprised of the recording disc and the cartridge main body housing the disc, or a tape cassette comprised of a tape reel fitted with a recording tape and a cassette housing the tape reel therein.
The sleeve casing 401 is formed by a sheet-shaped member of a synthetic material, such as polypropylene (PP) or polyethylene terephthalate (PFT), bent into a box one side of which is opened at 404 to provide a pouch-shaped structure, as shown in FIG. 1. The above-mentioned cassette, having the recording medium housed therein, is introduced into and held within the sleeve casing 401 via the opening 404. In general, the sleeve casing 401 is of a size just large enough to accommodate the cassette having the recording medium therein to hold the cassette by the force of friction between the outer surface of the cassette and the inner surface of the sleeve casing. The sleeve casing 401 has cut-outs 402,403 at forward ends of the major surfaces of the casing in continuation to the opening 404 for ease in taking out the cassette from the sleeve casing.
Meanwhile, since the sleeve casing is formed by bending a sheet-shaped member formed of paper or the synthetic resin, it can not be increased in thickness beyond a certain limit in order to retain its foldability, thus rendering it difficult to develop a sufficient toughness.
If the sleeve casing is used as a casing for holding a disc cartridge, the following problem arises. That is, if the casing for holding the disc cartridge therein is not of a sufficient toughness, the disc cartridge cannot be protected reliably. That is, if an external pressure is applied to the casing with the disc cartridge contained therein, the casing tends to be deformed easily. The result is the possible destruction or deformation of the disc cartridge contained in the casing under an external pressure. On the other hand, if plural disc cartridges contained in the respective casings be stacked one upon the other, the casings tend to be deformed under the weight of the overlying disc cartridges. The result is again the possible destruction or deformation of the disc cartridges.
Besides, the conventional sleeve casing for the disc cartridge are not provided with means for retaining the disc cartridge contained therein. Consequently, the disc cartridge tends to be disengaged out of the casing under shock or vibrations. If the disc cartridge be disengaged out of the casing while it is transported while being contained therein, there is a risk that the disc cartridge will fall on the floor or ground and be destroyed under the resulting shock.
Besides, since the disc cartridge is formed by bending a sheet-shaped material, the opening via which the cartridge main body is introduced into or taken out of the casing cannot be formed with ease to a predetermined shape in the casing. Besides, since the opening in the casing tends to be deformed, difficulties tend to be incurred in the operation of introducing the disc cartridge into the casing.
As a solution to such problem, it may be contemplated to form the casing of two casing halves, that is a top plate member and a bottom plate member, similar to two halves of the cartridge main body, these two plate members being abutted and connected to each other to complete a casing. In such case, these members are cast integrally by injection molding without the necessity of performing a bending or folding operation. The result is that these plate members can not be formed of a sufficiently tough material.
However, if the two plate members of the casing be connected together by set screws, the two plate members become complicated in structure. Besides, since female screws need to be provided so as to clear the disc cartridge, the top and bottom plate members become bulky in size as compared to the disc cartridge.
If the top and bottom plate members are connected together by so-called ultrasonic welding, the surface region of the plate members tend to be damaged by propagation of ultrasonic waves to detract from the appearance of the casing which should be as neat as possible. On the other hand, ultrasonic welding tends to scrape fused ribs formed along the junction line of the top and bottom plate members to produce debris which then tends to be left within the casing to be intruded later into the inside of the disc cartridge so as to be deposited on the disc within the disc cartridge to render it impossible to record and/or reproduce signals satisfactorily. Besides, the top and bottom plate members thus connected together by ultrasonic welding tend to be detached from each other due to insufficient durability under high temperature high humidity conditions.
If the top and bottom plate members are connected together using an adhesive, it takes some time until curing of the adhesive so that prompt connection cannot be achieved. Besides, it becomes necessary to control the amount of application of the adhesive so that an excess amount of the adhesive is not extruded from the space between the two plate members, thus leading to a complicated operation. In addition, a troublesome adhesive control operation is required to prevent the unused adhesive from being cured or to prevent the adhesive power from being lowered. The two plate members thus connected together by the adhesive tend to be detached from each other due to insufficient durability under high temperature high humidity conditions.
There may be occasions wherein the sleeve casing 401, shown in FIGS. 1 to 3, ready to be sold with a disc cartridge contained therein, is to be packaged with a film member of synthetic resin, such as an overlap film. This packaging is performed by so-called caramel wrapping, in which a sleeve casing 401 is introduced into the inside of an overlap film which is connected at opposite sides. Both end faces of the overlap film are folded inwards to form superposed portions which are heat-welded together to complete the wrapping. The heat welding is carried out by applying a heated ironing member, such as a heated metal plate, on the superposed portions of the overlap film. The overlap film is subsequently heat shrunk so as to be tightly affixed to the outer surface of the sleeve casing 401.
Meanwhile, since the overlap film is ultimately heat shrunk into tight contact with the outer surface of the sleeve casing 401, if any irregularities are present on the surface of the overlap film, the overlap film tends to be creased around these irregularities.
These creases not only detract from the appearance of the casing but also tend to catch the finger of a person handling the casing to produce rupture or severance of the heat-welded portions.
Since the above-mentioned cut-outs 402, 403 are formed in the sleeve casing 401, the outer lateral surface of the casing presents a step when the cassette, such as a disc cartridge is accommodated in the casing, as shown in FIGS. 2 and 3. That is, the major surfaces of the sleeve casing 401 present steps corresponding to the thickness of the casing as indicated by arrow d in FIG. 2. Besides, on the front side of the casing, there are formed ribs on both lateral sides of the cut-outs 402, 403 corresponding to the amount of projection of the major surfaces of the sleeve as indicated by arrow S in FIG. 3.